The invention relates generally to circulators for use in hydronic heating and cooling systems.
Such systems are often divided into zones, each zone serving a separate portion of a building and each zone controlled by its own thermostat. This allows a different temperature to be maintained in each area being heated or cooled. Zoning, i.e., diverting operating fluid into a given zone when necessary, is generally achieved using zone valves or circulators.
When zoning with circulators, a thermostatically-controlled pump is used to deliver operating fluid into each separate zone. As is most often found in the art today, a separate controller--containing a transformer and a relay--controls the circulator for each zone. The transformer steps line voltage (usually 115 volts) down, usually to 24 volts. A thermostat in the particular zone controls the relay, the coil of which operates at the stepped-down voltage. When the relay contacts close, line voltage is passed to the pump, thereby powering the circulator.
In some examples of the existing art, a controller consisting of one transformer and several relays--one relay for each zone--is utilized. A thermostat in each zone controls each relay, and each relay passes line voltage to the circulator in the given zone.
In each of these examples of the existing art, the circulator and controller are purchased and installed as independent parts. Electrical cabling is required between each controller and its associated circulator. Because the controller is separate from the circulator, it is usually manufactured to handle the largest possible circulator envisioned to be encountered. The transformer and relay usually have much greater electrical capability than necessary.
When zoning with circulators, it is also customary to install separate check valves on the outlet side of each circulator, both to isolate each zone from others and to prevent gravity circulation through the system. Gravity circulation occurs as the result of cooler, denser fluid in the return lines of a particular zone "falling," suctioning heated, less dense fluid into the given zone. The check valves are usually sweated into the supply line of each zone, downstream of the circulator.
Various forms of circulators are known. Some circulators employ a separate electrical motor coupled to a separate pump. Another form of circulator is the so-called "wet-rotor" circulator, in which the pump and motor are integrated, resulting in a more compact overall circulator unit. In a wet-rotor circulator, the rotor is supported within a rotor housing into which the fluid being circulated is allowed to enter (the fluid helps to lubricate the rotor bearings). The rotor housing is supported within a surrounding stator, which is sealed from the circulating fluid.